diff --git a/core/src/main/java/org/elasticsearch/common/unit/TimeValue.java b/core/src/main/java/org/elasticsearch/common/unit/TimeValue.java
index db8299cdc9ac4..ed67019c10399 100644
--- a/core/src/main/java/org/elasticsearch/common/unit/TimeValue.java
+++ b/core/src/main/java/org/elasticsearch/common/unit/TimeValue.java
@@ -326,7 +326,10 @@ public static TimeValue parseTimeValue(String sValue, TimeValue defaultValue, St
             return new TimeValue(parse(sValue, normalized, 2), TimeUnit.MILLISECONDS);
         } else if (normalized.endsWith("s")) {
             return new TimeValue(parse(sValue, normalized, 1), TimeUnit.SECONDS);
-        } else if (normalized.endsWith("m")) {
+        } else if (sValue.endsWith("m")) {
+            // parsing minutes should be case sensitive as `M` is generally
+            // accepted to mean months not minutes. This is the only case where
+            // the upper and lower case forms indicate different time units
             return new TimeValue(parse(sValue, normalized, 1), TimeUnit.MINUTES);
         } else if (normalized.endsWith("h")) {
             return new TimeValue(parse(sValue, normalized, 1), TimeUnit.HOURS);
diff --git a/core/src/test/java/org/elasticsearch/common/unit/TimeValueTests.java b/core/src/test/java/org/elasticsearch/common/unit/TimeValueTests.java
index 003d78ce42eca..4d0ac5257a31e 100644
--- a/core/src/test/java/org/elasticsearch/common/unit/TimeValueTests.java
+++ b/core/src/test/java/org/elasticsearch/common/unit/TimeValueTests.java
@@ -92,10 +92,6 @@ public void testParseTimeValue() {
                      TimeValue.parseTimeValue("10 m", null, "test"));
         assertEquals(new TimeValue(10, TimeUnit.MINUTES),
                      TimeValue.parseTimeValue("10m", null, "test"));
-        assertEquals(new TimeValue(10, TimeUnit.MINUTES),
-                     TimeValue.parseTimeValue("10 M", null, "test"));
-        assertEquals(new TimeValue(10, TimeUnit.MINUTES),
-                     TimeValue.parseTimeValue("10M", null, "test"));
 
         assertEquals(new TimeValue(10, TimeUnit.HOURS),
                      TimeValue.parseTimeValue("10 h", null, "test"));
@@ -115,6 +111,17 @@ public void testParseTimeValue() {
         assertEquals(new TimeValue(10, TimeUnit.DAYS),
                      TimeValue.parseTimeValue("10D", null, "test"));
 
+        // Time values of months should throw an exception as months are not
+        // supported. Note that this is the only unit that is not case sensitive
+        // as `m` is the only character that is overloaded in terms of which
+        // time unit is expected between the upper and lower case versions
+        expectThrows(ElasticsearchParseException.class, () -> {
+            TimeValue.parseTimeValue("10 M", null, "test");
+        });
+        expectThrows(ElasticsearchParseException.class, () -> {
+            TimeValue.parseTimeValue("10M", null, "test");
+        });
+
         final int length = randomIntBetween(0, 8);
         final String zeros = new String(new char[length]).replace('\0', '0');
         assertTrue(TimeValue.parseTimeValue("-" + zeros + "1", null, "test") == TimeValue.MINUS_ONE);